FIG. 18 shows a conventional light emitting device 211 which accommodates a light emitting chip 214, such as light emitting diode (LED). As sown in FIG. 18, the light emitting device has a mount portion 211a for mounting the light emitting chip 214 in the center of the top surface. The light emitting device further includes a base 212 of insulating material on which wiring conductors, such as lead terminal and metallized wiring, are formed for electrically connecting the mount portion 212a and the peripheral thereof with the interior and the exterior of the light emitting device, and a frame 213 made of metal, resin or ceramics, which is adhered onto the top surface of the base 212 and provided with a through-bore for accommodating the light emitting chip 214 in the center thereof.
The base 212 is made of ceramics, such as aluminum oxide sintered body (alumina ceramics), aluminum nitride sintered body, mullite sintered body, glass ceramics, or resin, such as epoxy resin. In the case of the base 212 being made of ceramics, metallized wiring layers are formed on the base by sintering at a high temperature metal paste including tungsten (W), molybdenum (Mo)—manganese (Mn). In the case of the base 212 being made of resin, lead terminals, made of copper (Cu) or iron (Fe)—nickel (Ni) alloy, are fixed inside the base 212 with the tip end thereof protruding when the base 212 is molded.
The frame 213, which is made of metal, such as aluminum (Al) or Fe—Ni—Co (cobalt) alloy, or ceramics, such as alumina sintered body, or resin, such as epoxy resin, is formed by machining, metallic molding or extrusion molding. In the center of the frame 213, formed is the through-bore which expands externally as it goes upward. In a case of enhancing an optical reflectivity of the inner surface of the through-bore, the inner surface is coated with metal, such as Al, using deposition or plating. The frame 213 is then adhered onto the top surface of the base 212 using soldering, such as tin solder or silver solder, or resin adhesives.
The wiring conductors (not shown) formed on the top surface of the base 212 and electrodes of the light emitting chip 214 are electrically connected with each other via boding wires (not shown). Then, after fluorescent layer 217 is formed over the light emitting chip 214, the inside of the frame 213 is filled with a thermally-cured transparent resin 215, thereby constituting a light emitting device which can externally emit light having a desired spectrum, which is converted in wavelength by fluorescent layer 217 from light emitted by the light emitting chip 214. Further, by selecting the light emitting chip 214 with an emission wavelength within an ultraviolet range of 300 to 400 nm and by adjusting the blend ratio of fluorescent material particles, exhibiting three primary colors of red, blue and green, contained in the fluorescent layer 217, color tone can be designed flexibly.
In general, the fluorescent material particles are in a powder form and it is difficult to form the fluorescent layer 217 with fluorescent materials alone, hence, the fluorescent layer 217 is typically formed by blending the fluorescent material particles into a transparent material of, e.g., resin or glass, and then coating it over the light emitting chip 214.    [PATENT DOCUMENT 1] JP 3065263, B    [PATENT DOCUMENT 2] JP 2003-110146, A